Wood preservation, known as traitement bois to the French, has been around for thousands of years. The earliest references to this practice go back to the very beginnings of history and are not presented in these early records as novel. It is likely that people have been using wood preservation methods ever since they began to use boats. They may have begun attempting to treat wood with preservatives long before that.
Pitch
One of the earliest known references to wood preservation appears in the Bible. In the book of genesis, God instructs Noah to build an ark and pitch it, presumably to better withstand the flood that allegedly occurred in prehistoric times. Pitch is made from plant resins or from petroleum. Given the location of the writing in the Bible, this was almost certainly a reference to pitch made from the various sources of petroleum that were accessible to ancient humans in the Middle East. The effect of applying pitch to a ship was to fill the seams between planks but also to protect the wood against the effects of constant exposure to water. Sea water, in particular, has a way of destroying wood.
Olive Oil
Alexander the Great, in the 4th century B.C. allegedly instructed his troops to dip pieces of wood in olive oil before using them to build the many bridges he built for purposes both civilian and military. There is no doubt that this is an effective preserver of wood. However, wood so treated must receive multiple treatments through the years because it is not permanent. People do still occasionally use vegetable oil to preserve wood today.
Tar
The ancient Romans preserved the ships of their navies by brushing the wooden exteriors with tar. This is essentially the same practice as using pitch. Tar, however, more often comes from tree resin. Its most important use was in waterproofing rather than preservation.
Creosote
Creosote is another preservative derived from plants. It merits its own specific mention, though, due to its popularity in the 19th century and early 20th century. Wood preservation really took off as an industry during this time period because train tracks began to cross the United States, Canada and Western Europe. The number of railroad ties was practically infinite and each had to be made to last, otherwise maintenance would have made railroads financially untenable.
Chemicals
When backyard projects among regular citizens increased after World War Two, manufacturers were hard pressed to find good preservatives in sufficient numbers for the expanding demand for wood preservation, which the French call traitement bois. They developed a number of chemicals that used mixtures of chromium, arsenic and copper to handle these tasks. Eventually the arsenic was reduced for removed for fear of toxic exposure.